“Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe?” -Stephen Hawking
One of the greatest discoveries of the 20th centuries was not only that there were just four fundamental forces describing all of nature, but that two of them — the electromagnetic and the weak force — unify into a single “electroweak” force at high energies. Given the equivalences between electric charges in the strong nuclear force sector and the electroweak sector, could there be a grand unification between those as well?
In a great theoretical development, Grand Unification Theories (GUTs) became all the rage, making bold predictions like additional bosons, flavor-changing neutral currents, and proton decay. But in the more than 30 years since their inception, the ideas of GUTs have all fallen flat, implying the question of whether the entire concept of unifying forces and interactions into larger groups and structures is completely wrongheaded.